Technical Field
The present invention relates to compounds for organic electric elements, organic electric elements comprising the same, and electronic devices thereof.
Background Art
In general, an organic light emitting phenomenon refers to a phenomenon in which electric energy is converted into light energy of an organic material. An organic electric element utilizing the organic light emitting phenomenon usually has a structure including an anode, a cathode, and an organic material layer interposed therebetween. In many cases, the organic material layer may have a multilayered structure including multiple layers made of different materials in order to improve the efficiency and stability of an organic electric element, and for example, may include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, or the like.
A material used as an organic material layer in an organic electric element may be classified into a light emitting material and a charge transport material, for example, a hole injection material, a hole transport material, an electron transport material, an electron injection material, and the like according to its function.
Currently, the power consumption is required more and more as size of display becomes larger and larger in the portable display market. Therefore, the power consumption is a very important factor in the portable display with a limited power source of the battery, and efficiency and life span issue also must be solved.
Efficiency, life span, driving voltage, and the like are correlated with each other. For example, if efficiency is increased, then driving voltage is relatively lowered, and the crystallization of an organic material due to Joule heating generated during operation is reduced as driving voltage is lowered, as a result of which life span shows a tendency to increase.
However, efficiency cannot be maximized only by simply improving the organic material layer. This is because long life span and high efficiency can be simultaneously achieved when an optimal combination of energy levels and T1 values, inherent material properties (mobility, interfacial properties, etc.), and the like among the respective layers included in the organic material layer is given. Therefore it is required to develop a light emitting material that has high thermal stability and can achieve efficiently a charge balance in the light-emitting layer.
Further, in order to solve the emission problem with a hole transport layer in a recent organic electric element, an emission-auxiliary layer is present between the hole transport layer and a light emitting layer, and it is time to develop different emission-auxiliary layers according to respective light emitting layers (R, G, B).
In general, an electron transferred from an electron transport layer to a light emitting layer and a hole transferred from a hole transport layer to the light emitting layer are recombined to form an exciton. However, since a material used in a hole transporting layer should have a low HOMO value, it mainly has a low T1 value.
However, since a material used in a hole transporting layer should have a low HOMO value, it mainly has a low T1 value. Due to this, excitons generated from a light emitting layer are transported to the hole transporting layer, resulting in a charge unbalance in the light emitting layer. Thus, light emission occurs in the hole transporting layer or at an interface of the hole transporting layer so that the organic electroluminescent device is reduced in color purity, efficiency, and lifespan.
Also, when using a material having rapid hole mobility for reducing a driving voltage, this is tend to decrease the efficiency. In an OLEDs, a charge unbalance in the light emitting layer is caused because of that hole mobility is faster than electron mobility, and reduced efficiency and lifespan is happened.
Therefore, an emitting auxiliary layer must be formed by a material what can solve the problems of an hole transport layer, having hole mobility (within the driving voltage range of the blue element of full device) to give the suitable driving voltage, high T1 energy value (electron block) and wide band gap. These requirements are not satisfied only by structural characteristics about a core of the emitting auxiliary layer's material. Therefore, it is necessary to develop of the material for the emitting auxiliary layer having high T1 energy value and wide band gap, to improve efficiency and lifespan of the organic electric element as combined core of material and characteristics of sub substituents appropriately.
In order to allow an organic electric element to fully exhibit the above-mentioned excellent features, it should be prerequisite to support a material constituting an organic material layer in the element, for example, a hole injection material, a hole transport material, a light emitting material, an electron transport material, an electron injection material, or the like, by a stable and efficient material. However, such a stable and efficient organic material layer material for an organic electric element has not yet been fully developed. Accordingly, there is a continuous need to develop new materials for an organic material layer.